The concept of modern triathlon originated in France at the beginning of the 20th century.

The newspaper L’Auto reported on the competition, called "Les Trois Sports", the condition of which was the passage of three stages: a 3 km race, a 12 km bicycle race and a swim across the Marne Canal. All three parts were overcome without any break. Over time, the distance needed to overcome increased.

1 stage:

Competitions begin with swimming. Mass start of all participants begins from the shore, pontoon or directly from the water (in a long triathlon). In case of a low water temperature (according to the rules of triathlon IRONMAN, it is usually not higher than 24.5 °С), it is allowed using wet suits/ diving suits up to 5 mm thick. Usually the swim goes along a triangular route, marked by buoys and ropes. For each arbitrary reduction in the length of the route, penalty points are awarded, and disqualification is also possible. Athletes can use any style of swimming that they prefer. Most often - it's a crawl.

2 stage:
Bike race

After leaving the water, athletes dress up in the transit zone, sit on bicycles and begin the cycle stage.

The food points are located at a distance, but technical assistance for professionals is prohibited. In the short triathlon, the usual road bikes are used for group races. In the triathlon IRONMAN, professionals prefer bicycles that are more similar to bicycles for a separate race in cycling. According to the rules of the International Federation of Triathlon (ITU), on road bicycles it is allowed to use short "plank bed" mounted on the steering wheel. «Plank bed» should not come forward for the line connecting the extreme part of the brake levers. «Plank bed» should either have no protruding parts at all, or its protruding parts should be connected by a jumper (plastic insert or just a few layers of insulation tape). Long «beds», like those used in cycling in individual races for time, are prohibited. This is understandable, since there is no special benefit from the "plank beds" in the short triathlon, in connection with the opportunity to improve the aerodynamics by simply hiding behind the back of the ahead going athlete. In the Olympic Triathlon (on the bicycle stage), leading/dominating is allowed, that is, the athletes can go in the group. In the triathlon Ironman, leading is forbidden; the athlete must ride a certain (approximately 10-15 meters) distance from a bicycle going ahead or a referee. Thus, the aerodynamics of the bicycle becomes quite important.

3 stage:

The main rule is that the athlete must move on its feet. Change between stages Observance of the order of change between the stages is strictly regulated (swimming -> bike -> running). Athletes should not interfere to other athletes (during the preparation of their bicycles or when changing clothes). They can manually move bicycles only within their designated area before and after ride. The helmet must be worn before the ride and removed after the bicycle is mounted on a special ramp or the designated place. Naked look during changing dress is prohibited by the rules of the competition according to the world standards. During the bicycle stage, the number plate must be on the athlete's back, during running stage — on the chest. The athlete must meet the time limit specified for each stage.